In order to alkylate aromatic hydrocarbons, it is necessary that an alkylating agent be present. Alcohols can serve as alkylating agents.
Therefore, in a feed stream of alcohols and aromatic hydrocarbons, the dehydration reaction of the alcohol occurs at the same time the alkylation reaction occurs. Since xylene, an alkylated aromatic, is a preferred product, the alkylation reaction is the preferred reaction and catalysts are chosen because of their ability to hinder the dehydration reaction and advance the alkylation reaction. The dehydration reation will occur, however, using the same catalyst.
The alkylation of aromatic hydrocarbons utilizing crystalline catalysts is well known in the art. The alkylation process is used to produce xylenes. Xylenes come in three isomeric forms: ortho-, meta- and para-xylene, the latter of which is of particular value in the manufacture of terephthalic acid which is an intermediate in the manufacture of synthetic fibers such as poly(ethylene terephthalate).
Prior art has shown the use of crystalline aluminosilicate catalysts in the production of xylenes through aromatic alkylation. One problem with some of these catalysts is that they tend to lose their activity quickly. These catalysts must also be selective. The reaction must favor particularly desired compounds, for instance para-xylenes over ortho-or meta-xylenes. It must also give reasonably high conversion rates.
Therefore, an object of this invention is to provide a catalyst that would not lose activity quickly.
Another object of this invention is to provide a selective catalyst. A preferred object of this invention is to provide a catalyst selective to para-xylene.
Another object of this invention is to provide a catalyst that provides high conversion rates.
Another object of this invention is to provide a catalyst that increases the production of alkyl-substituted aromatic hydrocarbons.
A specific object is to provide a catalyst for the production of xylene.
Another object of this invention is to provide a catalyst for the dehydration reaction of alcohols.
Other objects will become apparent from the following descriptions.